The noose of the title implies a tight knot, but the twists and turns of Grafton's latest plot are pretty loose. Not that the fans of self-reliant PI Kinsey Millhone's 13 previous alphabet appearances (from 1982's A Is for Alibi through 1996's M Is for Malice) are likely to object. This story takes Kinsey away from her Southern California coastal town of Santa Teresa to the small mountain community of Nota Lake in the Sierras. There, Selma Newquist hires Kinsey to ferret out the problem that had been seriously bothering her cop husband, Tom, before his recent death from a heart attack. Kinsey's efforts are soon stonewalled as the residents of Nota Lake unite, suggesting that the widow is being troublesome while the good-guy cop should be left to rest in peace. Kinsey wonders whether the townspeople might be right until she is seriously beaten up in her Nota Lake motel room. Focusing on finding the dead man's missing notebook, she follows his trail to a seedy hotel not far from Santa Teresa that he visited a few weeks before his death. While keeping a suspicious eye on the dead man's police partner and a few other local figures, Kinsey determines that Tom Newquist had been investigating an old murder near Nota Lake, which may have had ties to a similar, recent murder. Lots of coincidences, some over-the top characters, including a hyper-raunchy older woman, and some unprepared-for elements contribute to the rather chaotic climax. But Grafton's easy-reading, intelligent prose and her heroine's sharp humor, served up dark and wry, make up for a slew of plot weaknesses. 1,000,000 first printing; Mystery Guild main selection; Literary Guild selection; 18-city author tour. (May)